Roving Networks Bluetooth Serial Adapter, RN-240, RN-422, RN-270, RN-274 User Manual

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RN-BT-SRL-UM

Bluetooth Serial Adapter

USER MANUAL

© 2011 Roving Networks. All rights reserved.

RN-BT-SRL-UM-1.0 Version 1.0 11/11/2011

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OVERVIEW

Roving Networks offers a variety of Bluetooth serial adapters with different form factors and powering options (see Table 1).
These adapters enable wireless connection to any legacy serial port and support bi-directional RS-232 or RS-422 signaling
at a rate of up to 464 Kbps. To create a wireless cable replacement solution, simply attach the adapter to your device's
RS-232 or EIA-232/422 port and connect to it over Bluetooth. The transmission range is up to 330 feet (100 meters),
depending on environmental factors.

You can use these adapters as Bluetooth master or slave devices. The serial port profile (SPP) connection to the adapter
appears via a virtual COM interface. Data is sent and received on the client side as if a serial cable was connected to a real
COM port on the client.

You can also use the adapters in cable replacement mode in which two Roving Networks’ Bluetooth devices are paired
using configuration switches. The USB-to-Bluetooth (RN-USB-X) dongle has pairing switches and you can use it with the
Bluetooth adapter to create a wireless connection to a PC without using the PC’s Bluetooth stack. For more information on
cable replacement, refer to the Bluetooth Cable Replacement Application Note on the Roving Networks website at

http://www.rovingnetworks.com/Support_Overview.

Table 1. Bluetooth Serial Adapter Hardware Interfaces

Hardware Interface

RN-240

RN-422

RN-270

RN-274

RN-220XP

RS-232 ✔ ✔

✔

RS-422

✔ ✔

POWERING THE SERIAL ADAPTER

The Bluetooth serial adapters are powered using either rechargeable batteries, an external power cable, or using pin 9 of a
DB9 connector, depending on the adapter.

RN-240 & RN-422 Adapters

The RN-240 and RN-422 adapters are powered using either the DC power plug or via pin 9 of a DB9 connector.

RN-270, RN-274 & RN-220-XP Adapters

The RN-270 and RN-274 adapters are powered using two rechargeable AAA batteries, an external power cable, or using
pin 9 on a DB9 connector. The adapter has a red button on it’s top, which is a soft on/off switch. The adapter must have
batteries installed to function, even if the device is powered externally.

The RN-220XP adapter is powered with a LiPoly battery. The adapter has a toggle on/off switch.

WARNING: Do NOT use alkaline batteries when connecting the external power cable or applying power on pin 9 of the
DB9 connector.

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Turning the Adapter On & Off

To turn the adapter on, press the red button for 1 second until the green and blue LEDS begin flashing and then release it.
After a moment, the blue LED goes off and the green LED remain flashing to indicate the device is turned on and not
connected.

To turn the adapter off, press the red button for 1 second until the green and blue LEDs begin flashing and then release it.
All the LEDs turn off.

By default, the adapter automatically turns off if it is not connected over Bluetooth for more than 3 minutes (i.e., 180
seconds). You can control the sleep timer duration using the S+ command. For example, S+,600” sets the timer to 10
minutes.

Use the O command to display the sleep timer’s current settings.

Batteries & Charging

Only use NiMH rechargeable batteries when externally powering the adapter. Applying power with alkaline batteries
installed causes battery acid to leak and destroys the adapter (and surrounding environment).

The red LED turns on solid when external power is present. When the adapter is on, a blinking blue LED indicates low
battery. The battery life between charges depends on use. With typical usage the adapter should operate for at least 10
continuous hours between charges. Enabling sniff mode can extend the battery life (see Table 2).

You can apply external power from either the 5-V DC plug or pin 9 on the DB9 connector. The power plug is center pin
positive, outer cylinder ground. The input MUST be 5-V DC for proper battery charging. Higher voltages can permanently
damage the charger and battery.

Table 2. RN-270 Battery Life Table (Note 1)

Sniff Mode

Sniff Time (ms)

Battery Life

(with Status LEDs)

Battery Life

(without Status LEDs)

0

8 hrs, 20 mins

10 hrs

100

17 hrs

19 hrs, 30 mins

200

17 hrs, 30 mins

20 hrs

400

18 hrs

20 hrs, 30 mins

Notes:

1. The times shown are approximate and should be used as a reference only. Battery life varies depending on the type of batteries
used. New rechargeable batteries tend to have a longer battery life than older rechargeable batteries. Alkaline batteries, Energizer
batteries in particular, tend to last twice as long as rechargeable batteries.

Reducing Power when Connected

You can adjust the power used while connected by setting the sniff mode. By default, sniff mode is disabled and the radio
is active continuously when connected (using about 25 – 30 mA). With sniff mode enabled, the radio sleeps in very low
power mode (around 2 mA) and wakes up at specific intervals. Using sniff mode, the power savings can be quite dramatic.
To enable this mode, use the SW,<hex word> command. Refer to the Bluetooth Advanced User Manual on the Support
page of the Roving Networks website at http://www.rovingnetworks.com/Support_Overview for more information on using
sniff mode.

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Reducing Power when Disconnected

Low-power connection mode disables the Bluetooth radio and LED timers when the adapter is disconnected. In low-power
mode, the adapter cycles between active (discoverable and connectable) and low power deep sleep. This mode saves
considerable power when the module is waiting for long periods of time without a connection. The trade off is additional
latency when connecting or pairing. Refer to the Bluetooth Advanced User Manual on the Support page of the Roving
Networks website at http://www.rovingnetworks.com/Support_Overview for more information on using the low-power
connection mode.

STATUS LEDS

The adapters have several LED indicators. The green LED shows the Bluetooth connection status and the adapter’s
operational mode:

• When booting, the LED blinks two times per second.

• In configuration mode, it blinks ten times per second.

• When the module is in discoverable or idle mode, it blinks one time per second.

• When the module is connected, the green LED is on solid.

The yellow LED blinks when data is sent or received on the serial interface. This blinking does not indicate that data was
sent over the Bluetooth connection. If the yellow LED is not blinking when your device sends data to the serial port, the
connection or flow control may be set incorrectly.

Some versions of the RN-240 adapter have a red LED. This LED blinks when data is received over the RF link in low-speed
data mode.

OPERATING MODES

The Bluetooth adapter has several operating modes, which you set using the SM command in command mode:

• Slave (SM,1)—Default mode, whereby other Bluetooth devices can discover and connect to the adapter.

• Master (SM,1)—In this low-speed connection mode, the adapter makes connections when a connect command

(C), is received. This command can also contain the Bluetooth address of the remote device. If a device is not
specified, the adapter uses the stored remote address. The connection can be broken if the special break
character or string is sent (use the SO command to set the break character).

• Trigger (SM,2)—In this low-speed connection mode, the adapter makes connections automatically when a

character is received on the serial port. The connection continues as long as characters are received on either
end. The adapter has a configurable timeout (which you set using the ST command) that disconnects the
adapter after the specified number of seconds (1 to 254) of inactivity.

• Auto Master (SM,3)—In this mode, the adapter makes connections automatically on power-up, and re-connects

when the connection is lost. You can also enable this mode using switch 2. This mode is a high-speed
connection mode, and cannot be broken by software break characters.

NOTE: In all master modes, the device cannot be discovered or configured remotely over Bluetooth.

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CONFIGURATION SWITCHES

The adapters have small configuration switches on the top. You need a paper clip or small screwdriver to flip them.
Holding the adapter with the DB9 connector facing to the right, refer to Figure 1 for the switch numbering and on/off
positions.

Figure 1. Switches

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Table 3 describes the functions controlled by the switches.

Table 3. Switch Functions

Switch

Function

Description

1

Restore factory defaults

Turn on the switch, power up the adapter, and toggle the switch ON-OFF-ON-OFF-ON
to return the adapter to its factory settings. The green LED blinks quickly for a moment
and then continues to blink about once per second.

2

Automatic discovery

In slave mode, this switch sets a special class of device that is used by the master to
auto connect. If switch 3 also turned on, the adapter performs a search, stores, and
connects to a remote Roving Networks Bluetooth device that has switch 2 turned on.

3

Automatic master

With this switch turned on, the adapter acts as Bluetooth master and auto-connects to a
stored remote address. You must first set the Bluetooth address of the slave device
using the SR command or using instant cable replacement settings.

4

Default baud rate

With this switch turned off, the default 115 K baud rate is overridden by software baud
rate configuration commands. If this switch is turned on, the baud rate is 9600 and the
adapter ignores the software configuration.

4
3
2
1

On O

RN-270 & RN-274RN-240, RN-422 & RN-220-XP

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3
2
1

On O